Formation fluid sampler



"Z w @SS mm Nov. 16, 1965 R. 6. PETER 3,217,804

FORMATION FLUID SAMPLER Filed Dec. 26, 1962 2 Sheets-Sheet l INVENTOR,

Nov. 16, 1965 R. 6. PETER 3,217,804

FORMATION FLUID SAMPLER Filed Dec. 26, 1962 2 Sheets-Sheet 2 ActuatorForce, Tons s 7 e 9 I0 I! l2 l3 5 Borehole Diameter, Inches INVENTOR,

United States Patent 3,217,804 FORMATION FLUID SAMPLER Robert G. Peter,Houston, Tex., assignor to Halliburton Company, Duncan, Okla, acorporation of Delaware Filed Dec. 26, 1%2, Ser. No. 247,067 12 Claims.(Cl. 166-63) The present invention relates to sampling the fluid contentof earth formations, and, more particularly, to wireline apparatus fortaking samples laterally of a borehole piercing the earths formation ofinterest.

Such a device is useful in that formations about a borehole at variousdepth zones may be selectively sampled to determine fluid content.Information derived from such samples is useful, in turn, in evaluatingthe probable fluid productivity of such zones, and, hence, is a valuableaid in selecting from such zones, those having the best productionpotential for final completion.

Apparatus of this general type adapted for lowering into a borehole bymeans of a wireline and having provision for utilizing the hydrostaticenergy of its sampling environment for actuating power is well known andhas been long recognized as potentially providing a more facile,eflicient, and economic means of formation sampling than similarapparatus lowered by means of tubing string, for example. However, theprior art has not enabled the attainment of a sampling successefficiency commensurate with this potential because of the tendency ofdevices thus far provided to fail somehow during a sampling sequence.These failures in the main, may be traced to the design complexity ofthe prior art sampling devices.

Among the many causes of failure experienced with the rather complexprior art sampling devices of this general type, leakage past fluidseals predominates. Leakage, wherever it occurs, can cause failure ofthe immediate operations in which the tool is employed, either byrendering the actuating system of the device inoperative or by the lossof the fluid sample which the operation is to obtain. A failure of theactuator system, especially in the latter stages of the samplingsequence, when the device is still in anchored sealed engagement withthe borehole wall, may disable the device to the extent that it may notbe removed from the borehole without an expensive fishing operation. Itwill be appreciated that fishing operations are not sure of success, andtherefore, that the failure may result not only in the abortion of thesampling operation and the loss of the rather expensive sampling device,but possibly in the effective loss of the entire well.

Accordingly, it is the principal object of this invention to provide anew wireline formation fluid sampler device of improved generaleffectiveness, efliciency and reliability, and having a new constructonand mode of operation not provided in prior art devices.

Another object of the invention is the provision of a new and improvedsampler device initially controllable from the earths surface in itssample taking sequence by a first control link and ultimatelycontrollable in the latter portion of the sample taking sequence by asecond control link different in kind from the first link, whereby saidlatter portion of said sequence may be successfully carried out withoutregard for failure of said first control link.

Still another object of the invention is the provision of a formationfluid sampler device having a mode of actuation tending to assure moreeffective sealing engagement with the wall of the borehole.

A still further object of the invention is the provision of a formationfluid sampler device of simple maintenance and service requirement tothereby promote operating efliciency and economy.

3,217,804 Patented Nov. 16, 1965 Another object of the invention is theprovision of a formation fluid sampler device having a pack-offactuating system adapted to produce a substantially uniform initialpack-off sealing force against the wall of the borehole independently ofthe size of the borehole or of the hydrostatic pressure of the fluidtherein.

Still another object of the invention is provision of a formation fluidsampler embodying features which result in formation fluid samplingequipment smaller in size than comparable prior art tools ofapproximately the same capacity and general capability.

A further object of the invention is provision of a formation fluidsampler incorporating a new and improved sample chamber and sample flowcontrol system.

A still further object of the invention is the provision of a formationfluid sampler device employing a new and improved formation isolationpack-off means.

Another object of the invention is provision of a new and improvedactuation system for employment within a borehole environment which isadapted to produce substantially uniform forces independently of theborehole dept Still another object of the invention is the provision ofa formation fluid sampler device which produces an operative force ofsubstantially constant magnitude without regard for the degree ofmovement involved, but which on its retractive stroke produces adifferent magnitude of force.

A further object of this invention is the provision of an actuatorsystem for employment in a borehole environment which incorporates meansfor shock and acceleration control on both its active stroke andretractive stroke.

An object of the invention is the provision of a new and improved jetcharge carrier assembly adapted for operation in a high pressureborehole environment and which may be employed with great efliciency ina formation fluid sampler device, for example.

Other and further objects of the invention will be obvious upon anunderstanding of the illustrative embodiment about to be described, orwill be indicated in the claims, and various advantages not referred toherein will occur to one skilled in the art upon employment of theinvention in practice.

A preferred embodiment of the invention has been chosen for purposes ofillustration and description. The preferred embodiment is not intendedto be exhaustive nor to limit the invention to the precise formdisclosed. It is chosen and described in order to best explain theprinciples of the invention and their application in practical use tothereby enable others skilled in the art to best utilize the inventionin various embodiments and modifications as are best adapted to theparticular use contemplated.

In the accompanying drawings:

FIGURE 1 is a schematic illustration of a wireline formation fluidsampling device embodying the features of the present invention andshowing the same actuated and otherwise disposed for sample taking;

FIGURE 2 is a transverse sectional view taken along line 22 of FIG. 1;

FIGURE 3 is a transverse sectional view taken along line 33 of FIG. 1and showing the disposition of the wall engaging members of the devicewith respect to the walls of the borehole;

FIGURE 4 includes a number of illustrations or views which schematicallyillustrate the operative sequence of the actuator system employed in thedevice of FIG. 1;

FIGURE 5 is an enlarged partial sectional view of a sample chamberpiston assembly with pressure responsive braking system which may beemployed in the sample chamber of the device of FIG. 1;

FIGURE 6 is an enlarged sectional view of a sample chamber pistonassembly with a pressure responsive braking system which may bealternately employed or employed in conjunction with the braking systemillustrated in FIG. 5;

FIGURE 7 is an enlarged detailed sectional view of the pack-off assemblyof FIG. 1, illustrating the same as it may be disposed during movementtoward the sidewall of the borehole but not yet engaged therewith; and

FIGURE 8 is a graph illustrating the manner in which the setting forcevaries with borehole diameter on the actuation stroke. Also illustratedis a graph of the manner that the force available for retracting thewall engaging members varies with borehole diameter under the influenceof an arbitrarily selected borehole fluid pressure of 2000 psi.

Described generally, the formation fluid sampler device of the presentinvention, as shown in FIG. 1, comprises a downhole unit generallyindicated as 10 (and including a body 11) shown suspended from theearths surface within a borehole 12 by means of the wireline 14 fromsheave 17 and winch 18. The downhole unit 10 is adapted for actuationunder control from the earths surface exerted over wireline 14 to movewall engaging members or elements thereof into engagement with the wallof the borehole opposite a formation zone of interest and to isolate aportion of such zone and take a sample therefrom into a chamber providedin the unit. Actuation of the wall engaging members is provided for byan actuating system which is adapted to displace the wall engagingmembers outwardly with respect to the tool body by a first or actuationstroke powered by a pressurized gaseous medium contained in the unit andto withdraw the wall engaging members from the wall of the boreholeafter the sampling operation by a retractive stroke which is powered bythe pressure of the column of fluid which normally exists within aborehole.

It is to be understood that the showing of borehole 12 as an open holeis merely for the purpose of illustration and that the borehole unit 10is equally useful in cased holes penetrating the earths surface providedan isolation member suitable for employment in casing, i.e., without thesnorkel feature, is substituted for the open hole snorkel type formationisolation and sealing means illustrated and described.

With further reference to the drawing, the body 11 of the downhole unit10, beginning at its upper end, is comprised of a cable head section 20,a gas actuator section 30, a formation isolation section 50, a hydraulicactuator section 75, and a sample chamber section 80.

These sections generally divide the downhole unit 10 in a somewhatfunctional manner and, for that reason, will be useful in connectionwith the present description of the construction and operation of theformation fluid sampler of the invention.

Cable head section The cable head section 20 has as its function theprovision of means for attaching the downhole device to its suspendingwireline 14, the provision of means for connection of electrical powerand control circuits (not shown) within the downhole unit 10 to thecentral conductor 15 of wireline 14, in order that electrical power andcontrol signals may be communicated to such circuits from the earthssurface, and the provision of means for exerting surface control overcertain functions of the downhole unit by mechanical tension signaltransmitted over the wireline 14.

The body 11, within the portion defined by the cable head section 20, isprovided with a longitudinally extending bore 21 which communicates fromthe upper end of the body to a transversely extending bore 22 whichadmits any fluid which may be present in the borehole. The bore 21threadedly receives a sealing plug member 23 which serves to excludeborehole fluids from the bore 21 and thus provides, as will appear, anatmospheric pressure compartment 24 within the cable head section. Thesealing plug 23 is also provided with a longitudinal bore which forms aportion of the atmospheric compartment 24. A cable socket member 25extends in sealed slidable engagement through the bore 21 and sealingplug 23, longitudinally of atmospheric compartment 24 and further insealed slidable engagement with the bore 21 into the transverselyextending bore 22. The wireline 14, of course, is mechanically socketedwithin the upper end of the socket member 25. The socket member in soextending from the atmospheric compartment is exposed at both its upperand lower ends to the pressure of borehole fluid.

The end portions of the cable socket member which extend from theatmospheric compartment and are exposed to borehole fluids are of thesame cross-sectional area in order that there will be no tendency forthe socket member 25 to be shifted vertically because of pressureexerted thereon by borehole fluids. The cable socket member 25 isprovided with a flange 26 having an upper surface defining a seat for aspring 27 which is maintained in biased relation between the seat andthe upper end of the atmospheric compartment 24. The cable socket member25 is, in addition, provided wtih a stop flange 26', which is spacedfrom the flange 26. Flange 26 is normally maintained in biased contactwith the lower end of the atmospheric compartment 24 by the spring 27.The central conductor 15 of the wireline 14 extends in insulatedrelation through an axial bore in the cable socket member 25 andlaterally outwardly into the atmospheric compartment between the flanges26 and 26', where it is suitably connected with control and powercircuits (not shown). The connection of the wire within the atmosphericcompartment is provided with sufiicient slack to allow axial movement ofthe cable socket member 25. This occurs, as will appear, when thecontrol function of the cable head section is activated.

The spring 27 provided in the atmosphere compartment is of a size suchthat, when properly biased by adjustments of the longitudinal positionof the sealing plug 23 within the threaded longitudinally extending bore21, it maintains the cable socket in its normal position with its stopflange 26' in biased contact with the lower surface of the compartment24, with a force in excess of that required to support the entire weightof the downhole unit 10.

The cable socket member 25 is provided at its lower end with atransversely extending bore normally positioned in generally coaxialrelation with the transversely extending bore 22. The bore 22 terminatesat a blind end in which is provided a threaded receptacle which is alsodisposed generally coaxially thereof which communicates with a fluidflow passageway 28 within the body 11. A break valve 29 is provided insealed threaded engagement with the threaded receptacle and extendstherefrom into the bore 22 and through the transverse bore in the lowerend of the cable socket member 25. The break valve 29 normally excludesborehole fluid from entering the passageway 28 and the cable socketmember 25, in its normal disposition, imposes no load on the valve.However, when the downhole unit 10 is in anchored engagement with theborehole wall, as will be hereinafter described, upward tension appliedover the wireline above a predetermined amount moves the cable socketmember 25 upwardly with respect to the body of the downhole unit 10 andthe lower end of the socket applies a load to break the valve 29 at anotch 29' provided therein. When the valve is broken, the passageway 28is communicated with borehole fluids within the transversely extendingbore 22. The transversely extending bore 22 is provided with a screen 22which serves to retain the distal end portion of the break valve 29 whenthe same is broken otf at the notch 29' as just now described. As willappear from the description of the operation of the downhole unit 10,the break valve 29 functions responsive to wireline tension to bringabout the retraction sequence of the downhole device subsequent to theobtaining of the desired sample of formation fluids.

Gas actuation section As may be seen in FIG. 1, the gas actuationsection 30 is disposed immediately below cable head section 20. Thefunction of the gas actuation section is to provide force and power forurging wall engaging elements of the formation isolation section againstthe walls of the borehole so that a fluid sample be taken therefrom.

The gas actuation section 30 includes a generally cylindrical bufferfluid chamber 31 and a gas expansion.

chamber 32 coaxially disposed with respect to one another and spacedapart by a portion of the body forming an end wall common to bothchambers. A piston 31 is disposed for sealed slidable engagement withinthe chamber 31 and a piston 32' is disposed for sealed slidableengagement within the gas expansion chamber 32. The pistons 31' and 32are mechanically coupled together by a piston rod 33 which extends insealed slidable engagement through the common end wall of the twochambers. A rod 33, an extension of rod 33, depends from the face ofpiston 32' opposite the rod 33 and extends through the lower end wall ofthe chamber 32, in sealed slidable engagement therewith, where it isexposed to fluids of the borehole.

The piston 31 defines a buffer fluid space 31 at its rod end and a space31 for receiving borehale fluid at its other end within the chamber 31.The space 31", within the buffer fluid chamber 31, communicates with thefluid flow passageway 28 previously described.

The piston 32' defines, at that end from which the rod 33' depends, agas expansion space 32" and, at its other end, a gas equalization space32" within the gas expansion chamber 32. The function of these spaceswill be described hereinafter in connection with the description of theoperation of the downhole unit 10.

A chamber 34 is provided within the body of the downhole device 10 forreceiving a charge of pressurized gas for powering the active stroke ofthe downhole unit. A charging valve 35 is provided for convenience incharging the chamber 34 with a desired amount of gas for a given set ofoperating conditions. The valve 35 may be of any manually operated highpressure type such as a stop cock, for example. A passageway 36 isprovided for admitting the gas charge to the space 32". However,passageway 36, although shown communicating gas in FIG. 1 of thedrawing, is normally blocked by a setting valve 36. Although the valve36' may be of any type suitable for electric remote control from theearths surface, a normally closed valve of the type dis" closed incommonly assigned Patent No. 2,982,130 to McMahan may be employed.

An equalization valve 37 is provided in the gas actuation section forthe purpose of communicating the gas expansion space 32" with the gasequalization space 32' during the retraction sequence. Equalizationvalve 37 is piloted in its operation by the operation break valve 29.Equalization valve 37 includes a number of elements housed in a valvebore 38. The valve bore 38 communicates, by means of openings 38' and38", with the gas equalization space 32 and the gas expansion space 32".In addition, the valve bore 38 communicates, at its upper end, with thepreviously described passageway 28.

The bore 38 is sealed at its lower end by means of a plug member 39which defines a cavity in communication with the opening 38'. The plugmember 39 is also sealed with respect to the valve bore 38 at a pointintermediate the opening 38 and the opening 38". The upper end wall ofthe plug member 39, intermediate the upper end thereof and the cavityspace defined therein, constitutes a diaphragm thin enough to beperforated in a manner to be described, but strong enough to withstandthe pressures within the gas expansion space 32". It

6 is to be noted that the upper end of the plug member 39 extends withinthe valve bore 38 to a point short of blocking the opening 38" whichcommunicates from the valve bore into the gas equalization space 32".

A valve operator piston 40 is disposed within the valve bore 38 insealed slidable engagement therewith. The valve operator piston has anupwardly extending projection 41 which abuts the end of the valve bore38 in the normal position of the piston. The piston also has a tubularperforator extension 42 which depends from the lower surface of thepiston and is somewhat smaller in diameter than the diameter of thepiston per se. The perforator extension is suitably sharpened on itsdistal end to adapt the same to breach the upper end of the plug member39 when fonced thereagainst in the manner to be described. The junctureof the perforator extension 42 and the body of the piston 40 defines ashoulder which functions as a upper seat for a valve spring 43 which, atits lower end, bears on the upper surface of the plug member 39 tomaintain the piston 40 in its normal position biased against the upperend of the valve bore 38. A radial groove 44 communicates the bore ofthe perforator extension 42 with the valve bore 38.

The structure of the equalization valve 37, just now described, is suchthat fluid communication between the spaces 32" and 32, althoughnormally blocked by the end of the plug member 39, is establishedpursuant to the operation of break valve 29. This admits the pressure ofborehole fluid to the upper end of the valve operator piston 40 to forcethe same downwardly, overcoming the bias of the valve spring 43, tobreach the upper end wall of the plug member 39 by forcing theperforator extension 42 therethrough. When the qualization valve hasthus been operated, fluid communication is established from the gasexpansion space 32", via the opening 38', the cavity within the plugmember 39, through the bore of the perforator extension 42, the radialgroove 44, and thence, through the opening 38" into the gas equalizationspace 32" above the piston 32'. Once this communication has beenestablished, the pressure of the gas at either side of the piston 32 isequalized, and thus, exerts no tendency to displace the piston one wayor another. The advantages of this equalizing function as well as itsplace in the sequence of the operation of the downhole unit 10 will bebrought out hereinafter in connection with the description of theoperation of the downhole unit 10.

Formation isolation section Within the portion of the downhole unit 10designated as the formation isolation section 50, the body 11, which isotherwise generally cylindrical in form, bifurcates to provide twolaterally spaced longitudinally extending members 51.

The members 51 provide structural continuity of the downhole unit 10within the formation isolation section and connect the upper sections ofthe tool with those which are desirably located therebel'ow, and at thesame time, provide an open structure providing space for hous ing thewall engaging elements of this section as well as linkage provided fortheir actuation.

The portion of the rod 33', which extends from the gas expansion chamber32 and is exposed to the fluid within the borehole, extends between themembers 51 within the formation isolation section. The rod 33 isprovided with a cross-head enlargement 54, having projections 52 whichlaterally engage longitudinal grooves 53 provided in the members 51 forsliding engagement therein and for providing lateral support to the rod33'. A set of lower actuator links 55 are pivotally pinned and endconnected to the cross-head enlargement 54. In the normal retracted orunactuated disposition of the downhole unit 10, the rod 33, includingthe cross-head enlargement 54, is disposed at the somewhat lowerposition indicated by the dotted outline 54'. A set of upper actuatorlinks 56, similar to the lower links 55, are pivotally pinned and endconnected to the inner surfaces of the members 51 at pointslongitudinally spaced from the pins which connect the lower actuatorlinks 55 to the enlargement 54. A pair of upper links 56 and a pair oflower links 55 extending to the right of the body of the downhole unit10 are pinned together at their other ends by a pin 57 which provides anarticulated mounting for a formation isolation pack-off assembly 58. Apair of upper links 56 together with a pair of lower links 55, extendingto the left of the downhole unit 10, are pinned together at their otherends by a pin 59 which provides an articulated joint mounting for aback-up plate 60. The linkage pairs which respectively provide thearticulated mounting for the pack-off assembly 58 and for the back-upplate 60 comprise toggle mechanisms for applying actuating force to urgethe pack-off assembly 58 and back-up plate 60, respectively, into sealedand anchored engagement with the walls of the borehole.

When the formation isolation section is in its normally retracteddisposition with the pack-off assembly 58 and back-up plate 60maintained in close proximity to the members 51 and the enlargement ofthe rod 33' in its lowermost disposition as indicated at 54, the links55 and 56 of both mechanisms are initially disposed at an angle 6 ofabout 10 with respect to the centerline of the downhole unit 10. Thisinitial angle of the links assures that, when the linkage mechanisms areoperated in unison pursuant to upward movement of the rod 33 andenlargement 54, the pins 57 and 59 will be displaced outwardly withrespect to the downhole unit 10 in a positive fashion.

The outward displacement of the pins 57 and 59 is a function of theangle 0, as is the upward movement of the rod 33 and piston 32. Thus,the volume in space 32" related to the outward displacement of the pins57 and 59, and, hence, to the diameter of the particular borehole inwhich the unit may be set.

Curve A of FIG. 8 shows the forces exerted against the borehole wallduring the actuating stroke with variations in borehole diameter for atypical design wherein (a) the links 55 and 56 are effectively incheslong, (b) the piston 32 has an effective area of square inches, (c) theunit is charged with gas such that when the valve 36 is opened (beforeany movement of the piston 32), the gas occupies a volume of 8.4 cubicinches at 1200 psi. pressure, and (d) the upper surface of the piston 31has an effective area of 5 square inches. Curve B of FIG. 8 shows themanner that the force available for retracting the wall engaging membersvaries with borehole diameter upon the admission of borehole fluids at2000 p.s.i. to the space 31". This pressure would, of course, increasewith borehole depth, as does the plastering force which must be overcomeinitially during the retraction stroke.

Curve A of FIG. 8 shows that the setting force produced on the actuationstroke by the typical design is substantially constant within 7"l2borehole diameter range. This substantially constant setting forceapproaches the magnitude of about 3000 pounds. Such a magnitude hasproven satisfactory for producing good initial pad seals withoutdamaging the borehole wall formation face under a wide variety ofborehole and formation conditions. However, it will be apparent that ifthe downhole unit were charged to a greater or lesser gas pressure, acorrespondingly greater or lesser substantially constant setting forcewould be produced upon actuation. This choice of charging pressure, ofcourse, lends great flexibility to the use to which the actuation deviceof the invention may be put.

The pack-off assembly 58, best shown in FIG. 7, is mounted to links and56 of one of the toggle mechanisms, in pinned connection relationthereto, by means of the pin 57, as previously described. In making thisconnection, the pin 57 extends through a jet charge carrier and inletmember 61 which comprises a portion of the pack-off assembly 58. Themember 61 is fastened to a carrier plate 62 which, in turn at itsperipheral edges, is connected with a sheet-like sealing element 63 ofgenerally curved configuration having a front face adapted to engage andisolate a portion of the borehole wall. This sheet-like sealing elementmay be made of rubber, for example. The pin 57 is disposed with respectto the longitudinal extent of the carrier plate 62 and sealing element63 such that when the sealing element is urged into forced engagementwith the wall of the borehole, a center of applied force is establishedwhich bisects the longitudinal extent of the sealing element as shown inFIG. 7.

A rigid insert 64 is molded in the material of the sealing element 63 ata location such that the centerline of the insert is off-set withrespect to the center of force just now described. The member 61 isprovided with a jet charge carrier and inlet extension 65 which extendsin sealed relation through the carrier plate 62 and in sealed slidableengagement within a bore provided in the insert. The extension 65 isprovided with a bore 66 for housing a shaped charge 67 and a shapedcharge holder 68 for spacing the shaped charge from the walls of theextension 65. The shaped charge 67 is disposed within the extension withits hollow or shaped portion disposed toward the face of the sealingelement 63 and its booster end in abutting relation to a shoulder 66'defined within the bore 66. The shaped charge may be of any suitablehigh explosive material such as an RDX compound. The holder 68 generallyfills the space between the exterior of the shaped charge 67 and thewalls of the bore 66. The holder 68 is made of porous materialcharacterized by offering high impedance to the transmission of shockWaves from the shaped charge to the walls of the extension 65. Theporous material may be a suitably low density foam plastic materialhaving suflicient dimensional stability to space the explosive withinthe bore 66. Although a foamed plastic material may be preferable, anyother suitable material such as a foamed aluminum or sintered metalshaving high porosity and high impedance to transmission fo shock wavesmay be employed.

The bore 66 is greatly reduced in size as it extends rearwardly withinthe member 61 beyond the shoulder 66'. At a point beyond the shoulder66', the bore 66 is again enlarged slightly to receive a blasting cap 69which is electrically fired by a signal transmitted from the earthssurface over the suspending wireline 14. The rear end of the bore 66 isthreaded to receive a sealing plug to exclude borehole fluids fromentering the same. The end of the bore 66 extending forwardly of theshaped charge and holder is counterbored to sealingly receive a snorkelmember 70 which is adapted at its forward end for penetrating an earthformation when urged thereagainst. The snorkel member is secured in thecounterbore of bore 66 by means of a spring type locking ring. The bore66 is communicated with a flexible formation fluid sample line 71 bymeans of a passageway 72 extending therebetween.

The various parts of the pack-off assembly 58 are shown in FIG. 7 asthey would be disposed prior to engaging the wall of the borehole andprior to the firing of the shaped charge 67. When the sheet-like sealingelement 63 contacts the wall of the borehole, it is distorted to conformtherewith by the substantially constant force exerted through pin 57through the force center as has been described. The application of forcethen causes the extension 65 to move forwardly within the bore of therigid insert 64 and force the snorkel member 70 to penetrate the surfaceof the formation within the area sealed off from borehole fluids by thesealing element 63. With the pack-off assembly 58 thus deployed inpenetrating sealing engagement with the walls of the borehole, it isonly necessary to fire the blasting cap 69 in 9 order to detonate theshaped charge, to in turn, produce a characteristic jet stream andperforate the closed end of the snorkel member 70, as well as theformation therebeyond to establish drainage communication from theformation into the bore 66.

With the detonation and combustion of the charge 67, the outwardlyradiating shockwaves radially compress the porous material of the holder68 to form a dense liner within the bore 66. The bore 66, which isnormally blocked by the presence of the charge 67 and the holder 68, isopened for fluid to flow therethrough and, thence, into the passageway72 and the sample line 71.

Hydraulic power section Immediately below the formation isolationsection 50, the longitudinal members 51 merge with a cylindrical portionof body 11 which houses the hydraulic power section 75. The hydraulicpower section 75, together with the buffer fluid chamber 31 located inthe gas actuation section, is a part of a shock absorbing system whichmoderates the shock forces incident to setting and retraction of thewall engaging members of the formation isolation setcion, i.e., pack-oftassembly 58, and back up plate 60. Also, the hydraulic power sectionfunctions as the proximate means for retraction of the wall engagingmembers from the walls of the borehole. This section includes agenerally cylindrical fluid chamber 76 coaxially disposed with respectto the centerline of the downhole unit 10. The rod 33', which extendsthrough the formation isolation section 50, extends in sealing slidableengagement through the upper wall of the just-mentioned fluid chamber76. A piston 76' is disposed in sealed slidable engagement within thechamber 76 and is mechanically coupled to the end of the rod 33.

The piston 76' defines, toward its rod end within the chamber 76, aspace 76 and, at its other end, a space 76' which contains a gas atnegligibly low pressure. The space 76" is communicated upwardly throughthe formation isolation section 50 and into the gas actuation section 30by means of a fluid passageway 77 to the space 31" defined below thepiston 31' in buffer fluid chamber 31. As shown in FIG. 1, thepassageway 77 may extend coaxially through the rod 33, the piston 32,and the rod 33 in making this communication. It will be noted that thepassageway 77 is provided with a restriction 78 to impede the rate atwhich fluid may transfer through the passageway 77. This fluid transfer,as will be brought out hereinafter in the description of the operationof the downhole device 10, takes place with and in proportion to vertical displacement of the mechanically connected movable elements whichinclude piston 31, rod 33, piston 32, rod 33, and piston 76'.

At the upper surface of the hydraulic power section 75, the flexiblesample line 71 connects with a passageway 79 which extends downwardlythrough the hydraulic power section to communicate with a cylindricalchamber 82 in the sample chamber section 88, located therebelow.

Sample chamber section The passageway 79, in entering the sample chambersection 88, communicates through a normally open remotely controllablevalve 81 which, responsive to a suitable signal communicated from theearths surface over the wireline, may be actuated to shut in any samplefluid which has been received within the chamber 82 during a sampletaking operation. Although the valve 81 may be of any suitable type, ithas been found that a normally open valve such as disclosed in commonlyassigned US. Patent No. 2,982,130 to McMahan may be employed toadvantage.

A rod member 83 extends longitudinally within the chamber 82 in parallelrelation to the walls thereof and is securely fastened to the upper orfluid inlet end thereof. Although this fastening may be accomplished byany means which is capable of withstanding tensile loads approaching theyield strength of the rod member, a threaded fastening, as illustrated,is to be preferred because of its simplicity. The lower end of the rodmember is maintained in alignment with the upper end thereof by a recessprovided in a closure cap 84 which seals the lower end of the chamber82. The cap 84 is removable to provide a convenient access to thechamber in order that the same may be cleaned and redressed as will bedescribed.

A piston assembly is provided in sealed slidable engagement with thecylindrical walls of the chamber 82 as well as with the exterior of therod member 83. The function of the piston assembly, in conjunction withthe rod member 83, is to constrain sample fluids entering the chamber 82thereabove to do work in overcoming a braking resistance provided by thepiston in proportion to the pressure of sample fluids within thechamber.

For the purpose of performing this function, the piston assembly 85 isprovided with one or more pressure responsive force mechanisms forurging a cold working tool into working engagement with the rod member83 to a depth in proportion to the pressure of the fluid within thechamber. Three pressure responsive force mechanisms (only two are shown)are incorporated in the piston body 85 in angularly spaced dispositionabout the rod member 83 to secure a distributed braking force andminimize any tendency for the piston assembly to cock or bind.

The type of pressure responsive force mechanisms employed in pistonassembly 85 is best seen in FIG. 5 to comprise a bore within the body 85in which a pressure sensing piston 86 is disposed in sealing slidableengagement. The piston 86 has a rod extension 87 which extends throughthe body 85' and receives a biasing spring 88 and retainer nut 89. Theselatter elements serve to maintain the sensing system 86 in sealedrelation within its bore and yet permits its relative movement therein.The spring may desirably vary in rate with displacement in a manner tocompensate for variations in mechanical advantage of the toggle linkageto which the piston 86 provides a motivating force input as will appear.

A transverse slot with load-bearing surface 90 is provided in the rodextension 87 for the purpose of applying the differential forcedeveloped across piston 86 through a knee joint 91 of a toggle linkagesystem disposed within the body 85, generally transversely of the rodextension. One link of the toggle has its distal end socketed in thebody 85 in a manner to permit angular displacements of the link, but tooppose further radially outward displacement of that end relative to therod extension 87. The other toggle link bears on an indenter 92 which isguided for movement within body 85' in a radial direction with respectto the rod member 83. The indenter is preferably made of sinteredcarbide so as to minimize the tendency to gall the rod member.

The indenter 92 preferably has a generated curved end which, responsiveto the thrust developed in the toggle linkage, brinells the rod member83 to a degree proportionate to the differential pressure forcedeveloped across the piston assembly 85 between sample fluid pressure inthe inlet end of the chamber 82 and the pressure of compressible gas ofnegligible value at the other end of the chamber. As the piston assemblyis displaced with respect to the rod member 83, the indenter 92 coldworks a groove 93 into the surface thereof and imposes a braking load onthe piston in proportion to the degree of brinelling of the rod member83.

The generated curved indentor shape provides a twofold advantage in thepiston braking system in which it is incorporated. First, the generatedcurved end may be shaped so as to tend to compensate for non-linearforce effects introduced by the toggle linkage. Second, the generatedcurved end positively reduces indentor depth in proportion to reductionsin sensed pressure by riding up the curve formed at the leading edge ofthe groove in a cam-like manner as the piston assembly traverse causesrelative movement therebetween.

As the piston assembly 84 is displaced downwardly within the chamber 82,the indenter 92 forms a cold work groove 93 in the rod 83. This formingimparts a braking force which varies with the pressure of sample fluidsbetween the piston assembly 84 and the chamber 82 which subtracts fromthe force otherwise available for displacing the piston assembly.

Thus, at any given pressure of fluid within the chamber 82, indenter 92is forced to brinell the rod member 83 to an extent such that this samepressure acting on the effective area of the piston assembly 85 isresisted by a braking force arising from the longitudinal displacementof the indenter 86 along the axis of the rod member to form the coldworking groove 93 therein. The net force tending to displace the pistondownwardly within chamber 82 is equal to the sample fluid pressure timesthe effective area of the piston assembly 84 minus the braking forcethus applied by the pressure responsive mechanism incorporated withinthe piston assembly. Since the displacement of the piston assembly withtime is a function of this net force which tends toward a constantvalue, the flow of fluids entering the sample chamber will vary in asubstantially uniform manner. If the pressure of the fluid within thechamber increases during the displacement of the piston, the brakingforce will correspondingly increase and tend to maintain this uniformmanner. Conversely, if the pressure in the chamber decreases, theindenter tool will withdraw from the member 83 a proportionate amount,thus reducing the braking force, and tend to maintain the uniformmanner.

The piston assembly 84 is provided about its exterior periphery with aplurality of O ring type seals 94 which assure a frictional resistanceto displacement of the piston assembly 84 which is substantial to theextent that the piston will not displace downwardly in the cylinder 82responsive solely to the force of gravity. This frictional resistance todisplacement of the piston within the cylinder also assures thatindenter 92, by virtue of there being less frictional resistance tomovement of the sensing piston 86, will respond to changes in thepressure of fluid in the chamber 82 prior to the displacement of thepiston assembly responsive thereto.

It will be apparent that the braking force is transferred from thepiston assembly 84 to the upper end of the chamber 82 by a tensileloading developed within the rod member 83. The rod member 83 must havea tensile yield strength to withstand any such loadings as is likely tooccur in service. Further, the material of the rod member 83 should havea brinell hardness or resistance to penetration of the indenter suchthat when the indenter is actuated by the sensing pistons and togglelinkages of a particular design, the braking forces developed willapproach, but fall somewhat short of, the product of the fluid samplepressure within the chamber times the effec tive area of the pistonassembly. The rod member 83 is deformed by the cold working to a pointwhere it is not again usable. Consequently, the rod member 83 should notonly exhibit the aforementioned qualities, but should be of justifiableexpense. Cold rolled steel rods have been found to provide the requiredphysical properties and the desired surface smoothness for obtaining anO ring seal.

A modified form of piston assembly, which may be used interchangeablywith the piston assembly 85, is shown in FIG. 6 to be comprised of apiston body 85", a pressure sensing piston 86, a spring 88, a nut 89,and a toggle linkage identical to that employed in the assembly of FIG.5. Although the construction of the piston assembly of FIG. 6 isgenerally similar to that of FIG. 5, the piston body 85" is slightlymodified to provide for the guidance of a cutting tool 96 in a radialdirection with respect to the rod member 83 in the stead of the indenter92 provided in FIG. 5. The guidance passageway, as

well as the cutting tool 96 guided thereby, is desirably of squarecross-section so that rotation of the cutting tool with respect to theguidance passage is prevented. The cutting tool 96 bears the samerelation to the toggle linkage as the indenter 92 bears thereto in FIG.5. The toggle linkage of FIG. 6 is actuated by a pressure differentialdeveloped across the sensing piston 86 in the same manner as has beendescribed in connection with its counterpart of FIG. 5 to move thecutting tool 96 into varying degrees of cutting engagement with the rod83 of FIG. 6 responsive to variations in pressure sensed by the sensingpiston. The cutting tool 96 is preferably made of a sintered carbidematerial and is sharpened to provide a conventional relief angle and aslightly negative rake angle. The negative rake angle is advantageous,not only because it necessitates the application of more force to make agiven cut, but in addition, enables the tool bit to back out of the cutwhen the axial force on the tool bit is reduced in the manner explainedin connection with the indentor type brake mechanism of FIG. 5.

In addition to the tool bit 96 in the mechanism of FIG. 6, the pistonbody is provided with a passageway 97 which functions to curl the chipas it is removed by the rake surface of the tool bit 96 and to conveythe curled chip through the piston and into the sample fluid end ofchamber 82.

The piston assembly of FIG. 6 functions to cold work the rod member 83by removing a chip 98 therefrom as the piston assembly is displaceddownwardly in the sample chamber responsive to the in flow of formationsample fluid. As the piston is displaced, the depth of cut of the tool96 varies in accordance with the pressure of formation fluids exerted onthe sensing piston 86 to machine a longitudinal groove 99 in thematerial of rod member 83. It will be appreciated that the brakingresistance applied to the piston will be proportionate to the depth ofthe cut being made by the cutting tool 96 which is, in turn,proportionate to the pressure of the sample fluid within the chamber 82.

It will be apparent that the two methods of cold working shown, i.e.,cutting and displacing the metal of the rod member 83, may be employedtogether within the same piston body to provide a piston assembly whichcold works the rod 83 both by brinelling with indenters such as 92, aswell as by cutting a groove therein by means of cutting tool such as 96.Such combinations including other methods of cold working may bedesirable in tailoring the braking resistance offered to the traverse ofthe piston assembly to best fit the requirements occasioned by boreholeconditions in different operating areas.

Operation Assuming that the downhole unit 10 has been previouslyemployed in a sample taking operation, before it can be again soemployed, it should be cleaned and redressed to replace the previouslyspent expendable elements. These expendable elements include break valve29, plug member 39, the explosive and expendable elements associatedwith the jet charge carrier and inlet member 61, as well as thoseassociated with setting valve 36' and sample shut in valve 81. Inaddition, the sample chamber should be thoroughly cleaned and a new rodmember 83 installed therein with the piston assembly 85 positioned atthe upper end thereof. The piston assembly is maintained in thisdisposition by the frictional engagement of its various 0 ring seals.Further, the chamber 34 would be charged with an appropriate amount ofgas through charging valve 35 in order that pressure energy will beavailable for powering the actuating stroke of the gas actuator section30 to a desired degree. Assuming that all the foregoing necessaryredressing steps have been taken, the downhole unit 10 is then loweredwithin the borehole by means of the wireline 14 to the point where thepack-off assembly 58 is disposed opposite the formation from which atest is desired.

Next, the downhole unit is actuated by opening the setting valve 36'pursuant to an electrical signal transmitted to the earths surface overthe wireline 14. This communicates the charge of gas within the chamber34 to the space 32" beneath the piston 32', and the pressure of the gasmoves the piston 32, as well as the pistons 31' and 76' which arerespectively interconnected therewith by rods 33 and 33, in an upwarddirection with respect to the body 11. With this movement, thecross-head 54 is displaced upwardly from its initial position, indicatedas 54', into the position shown to actuate the toggle linkages and forcethe back up plate 60 and pack off assembly 58 respectively intoanchoring and sealing engagement with the walls of the borehole 12 asshown in FIG. 1. During the displacements of the various parts of thedownhole unit during the actuating stroke, the acceleration or shockforces imposed by the displacement are limited in magnitude by themetered transfer of the buffer fluid initially filling the space 76",from within the hydraulic power section 75 into the space 31" beneaththe piston 31'. The displacements of the parts continue, within limits,until the wall engaging members, i.e., back up plate 60 and pack offassembly 58, contact and respec tively set and seal against the wall ofthe borehole.

The details of the actuating stroke including the manner of coaction ofthe various pistons and cylinders involved, as well as movements offluids with respect to these various coacting cylinders, is perhaps moreclearly, albeit more schematically, shown in FIG. 4, views A through C.In these views of FIG. 4, the same reference numerals have been appliedto parts which are the counter parts of similarly numbered elements inFIG. 1. In view A, which schematically shows the various pistons intheir normal unactuated position within their respective chambers, itwill me noted that the setting valve 36' is closed and that the variouspistons are disposed toward the lower end of their respective chambersand that the space 76" above the piston 76' is filled with the bufferfluid. The buffer fluid, of course, may be any suitable substantiallyincompressible fluid. Views B and C of FIG. 4, respectively,schematically show the device of view A in successive dispositions whichthe same might assume during a typical actuating stroke. It will benoted that in these later two views, the setting valve 36' is open, thecharge of gas is being admitted therethrough from the chamber 34 intothe space beneath the piston 32' to exert a force thereon and move allthe various pistons and rods in an upward direction. It will also benoted in views B and C that the buffer fluid in the space 76 is beingtransferred, at a metered rate determined by the restriction 78 in thetransfer path, upwardly into the space 31" beneath the piston 32. Theupward displacement of the pistons and rods will, of course, be haltedas soon as the toggle linkages bring the back up plate 60 and pack offassembly 58 into forced engagement with the walls of the borehole.

When the pack off assembly (see FIG. 7) is moved into actual engagement,the sealing element 63 will contact the wall first in being urgedthereagainst by the carrier plate 62. The toggle linkage will continueto move the carrier plate 62 outwardly and tend to compress and conformthe sealing element 63 into sealing engagement with the borehole wall.With this latter movement, the jet charge carrier and inlet extension 65will be moved with respect to the insert 64 in the face of the sealingelement 63, and displace the snorkel member 70 beyond the face of thesealing element and cause the snorkel member to penetrate any boreholewall filter cake and the formation of the borehole wall to establish agood, albeit closed, fluid communication therewith.

Next in the operating sequence, blasting cap 69 is fired pursuant toelectrical signal transmitted from the earths surface to detonate theshaped charge 67 which, in turn, forms a penetrating jet stream directedalong the axis of the snorkel member 70. The jet stream penetrates thatportion of the snorkel member and the formation therebeyond to establisha laterally extending formation drainage or flow passagewaycommunicating the jet charge carrier and inlet extension 65.

Of the total energy released with the detonation of a jet charge such as67, the amount of energy which is concentrated in the directed jetstream is a rather small percentage of total, on the order of less than10% of the total energy. The balance of the released energy emanates aspherically divergent shock wave which, in the instant application, mustbe contained within the confines of the rather small jet charge carrierand inlet extension 65 without damage thereto which would destroy itsutility as a fluid conducting element of the fluid flow path between theformation and the sample chamber 82. Because the shock wave impedance ofthe holder 68 is high in comparison to the characteristic shock waveimpedance of the explosive, there is an impedance mismatch, and thus theholder 68 functions during the detonation as a shock wave reflector, atits interfaces in common with the jet charge, which reflects the radialshock wave and tends to contain the same within the material of thecharge. Secondly, the holder 68 functions as an inefiicient shock wavetransmission media, i.e., one offering high impedance to thetransmission of shock waves therethrough. Thirdly, the holder 68functions as a means for extracting work and energy from the shock wavesby forcing them to do work in compressing and compacting its porousmaterial against the inner walls of the sample inlet and jet chargecarrier section. All three of these effects work to effectively protectthe sample inlet and jet charge carrier extension from the full brunt ofthe shock wave energy it must contain.

With the compaction and compression of the porous material against theinner walls of the carrier extension, the porous material is transformedinto a dense thin liner therein to open fluid communication from theformation into the fluid sample path communicating with the samplechamber 82.

With the fluid flow path thus opened to the sample chamber, formationfluid may communicate thereto to the top side of the piston assemblywhich is initially positioned near the upper end of the chamber 82. Asformation fluid enters the chamber above the piston and developspressure therein, the piston assembly will be urged downwardly under theinfluence thereof. However, the pressure in the chamber will also besensed by the sensing piston 86 within the piston assembly and exert aresisting or braking force on the rod member 83 to oppose the force offormation fluid urging the piston assembly 85 downwardly. Although theresisting braking force is proportionate to the force urging the pistonassembly 85 in a downwardly direction, it never exceeds it, andconsequently, the braking force merely reduces the net eifective forcewhich displaces the piston downwardly as the sample enters. Thisreduction in the net force moving the piston assembly 85 works to limitor moderate the rate that sample fluids may enter the sample chamber 82.This moderation of the flow rate tends to minimize the problem ofplugged sample lines arising from formation being carried into thesample line by high fluid velocities which would otherwise be developedacross the formation pad seal interface.

After the piston assembly has made its full traverse of the chamber 82responsive to the filling of the same with formation sample fluids, theshut in valve 81 is closed responsive to an electrical signalcommunicated thereto from the earths surface to complete the sampletaking phase of the operation of the downhole unit 10. However, prior toremoval of the downhole unit 10 from the borehole, the wall engagingmembers of the downhole unit, i.e., back up plate 60 and pack offassembly 58 must be disengaged from the borehole Wall and retracted totheir initial disposition adjacent the longitudinal members 51.

To initiate the retraction, a predetermined tension is exerted on thewireline 14 in excess of the weight of the downhole unit 10. Thistension is resisted by the anchored engagement of the wall engagingmembers and works to displace the cable socket 25 upwardly to compressthe spring 27 and break the break valve 29 at the point defined by thenotch 29. The breaking of the valve permits borehole fluid pressure tocommunicate with the space 31 and the upper surface of the piston 31.The breaking of the valve 29 also pilots the operation of the equalizingvalve 37, in that the borehole fluid pressure is also communicated tothe upper surface of the valve operator piston 40 to force the samedownwardly, compressing the valve spring 43, and causing the perforatorextension 42 to penetrate the upper end wall of the plug member 39. Thispenetration establishes a gas flow communication between the gasexpansion space 32 and the gas equalization space 32" to equalize thepressure force of gas across the piston 32.

The force of formation fluid exerted on the top side of piston 31' iscommunicated mechanically through the piston to create within the bufferfluid in the chamber 31", immediately therebelow, a fluid pressure onthe order of magnitude of the pressure of borehole fluids. This createdpressure then causes the buffer fluid in space 31" to transfer back overthe restricted path into the space 76" within the hydraulic powersection 75 from whence it was displaced during the actuation stroke.Because the buffer fluid contained below the piston 31 is substantiallyincompressible, no appreciable mechanical force is directly applied tothis piston insofar as motivation of the retraction stroke is concerned.However, as the buffer fluid transfers back to the space 76", responsiveto the created pressure under the piston 31', the pressure in the space76 builds up and acts on the top surface of the piston 76 to exert atension force in the rod 33 and pull the cross head 54 downwardly toretract the wall engaging members. The coaction of the various cylindersand pistons and rods, including their movements occasioned by the justnow described transfer of buffer fluid back to the space 76", is perhapsmore clearly shown in the simplified schematic view of the retractionstroke of FIG. 4D.

Of course, with the downward stroke of the piston and rod members, thetoggle linkages will be restored to their retracted dispositions asshown by the dotted outline in FIG. 1 with a force proportionate to thehydrostatic pressure of borehole fluids. It is to be noted that althoughthe borehole fluid is admitted to the space 31', the actual motivatingforce during the retraction stroke is applied by the pressure of thebuffer fluid within the space 76" above the piston 76 to thereby placethe rod member extending through the formation isolation section under atensile loading. Rod member 33' is also under a tensile loading on itsupward or actuating stroke as motivated by the pressure of the gaswithin the chamber 32". The fact of tensile loading in the rod 33 onboth its actuating and retraction stroke permits the employment of a rodof much smaller diameter and slenderness than would be required ifloaded in compression.

The retraction stroke just now described completes the samplingoperation so that the downhole unit may be withdrawn from the boreholeby means of the wireline 14. At the earths surface, the sample containedin the chamber 82 may be removed by any convenient well known means (notshown), e.g., a drain cock.

It will be apparent in the light of the foregoing description of thestructure and operation of the actuatorretractor and connected togglelinkages that the system provided by this invention extends the wallengaging elements of the formation isolation section into engagementwith the wall of the borehole with the force which is substantiallyuniform regardless of the size of the borehole in which it may be set.The force necessary to provide an initial seal between the pad assembly58 and the wall of the borehole is generally significantly less than theforce required to remove the same therefrom after a sampling operation.The force to remove is directly related to borehole depth, in that thedifferential force between hydrostatic pressure of the borehole fluidand the pressure of formation fluid is exerted on the back face of thesealing element 63 to, in effect, plaster the same against the wall withhigh force. Because of this plastering force, a higher force is requiredto break the seal of the pad assembly than is initially required to setthe same. The device of the invention provides an actuatorretractormechanism which produces the relatively low force required to obtain aninitial seal on its actuating stroke and which produces force whichvaries with the hydrostatic pressure of the borehole on its retractingstroke.

During the retraction stroke, the actuator initially moves the carrierplate 62 with respect to the sealing member 63 and withdraws the jetcarrier and inlet extension 65 from the insert 64 enough to break thefluid seal therebetween. This performs the function of equalizing thepressure of the area sealed off by the seal member with the pressure ofborehole fluids. This equalization tends to destroy or reduce theplastering force and thus facilitates retraction of the pack offassembly. Borehole fluids communicate to the space between the carrierplate 62 and the sealing member 63 through passageways provided in thesealing member near its attachment to the carrier plate.

Thus, it has been seen that the present invention provides a new andimproved formation fluid sampler of improved performance, efliciency,economy, and safety, which incorporates an actuator-retractor mechanismwhich yields forces better suited for the service requirements. Further,it has been seen that the mechanism is shock buffered on both itsstrokes to minimize any destructive shock effects due to accelerationsin its movement. Further, it has been seen that the sampler of theinvention enables the construction of devices which are smaller inoverall physical size than prior art devices, but yet have comparablesample taking capacities. It has been further seen that because of thereduction of the number of control functions which must be exerted overthe downhole unit via the cable from the earth's surface, particularlyas to control functions involved during the preparing of the downholedevice for removal from the borehole, a simpler and consequently morereliable unit has been provided.

As various changes may be made in the form, construction, andarrangement of the elements herein disclosed without departing from thespirit or scope of the invention, and without sacrificing any of itsadvantages, it is to be understood that all matters herein are to beinterpreted as illustrative and not in any limited sense.

What is claimed is:

1. A device for obtaining samples of the fluid content of formationstraversed by a borehole containing a column of fluid comprising: asupport adapted to be suspended in a borehole by means of a wirelinefrom the earths surface; a chamber in said support for receiving a fluidsample; means mounted on said support adapted to isolate an area ofborehole wall when engaged therewith; motive means in said support formoving said means into engagement with the wall of the borehole; aninlet member in the first-mentioned means having walls adapted forexposure to and for withstanding the pressure of said column of fluid; acharge of explosive material, shaped for producing a jet stream whendetonated, said charge being housed in said inlet member in spacedrelation to said walls and normally closing said inlet member andpreventing borehole fluids from entering said chamber; means in saidinlet member for detonating said charge; a spacer disposed about saidcharge within said inlet for maintaining said spaced relation comprisedof porous material; and a fluid channel communicating between said inletmember and said chamber, said charge when detonated adapted to radiallycompress said porous material against the walls of said inlet member,whereby fluid communication is established through said inlet memberbetween the formation within said isolated area and said chamber.

2. A device for obtaining samples of fluid content of formationstraversed by a borehole comprising: a support adapted to be suspended ina borehole by means of a wireline from the earths surface; a cylinder insaid support for receiving a fluid sample; means mounted on said supportfor isolating an area of borehole wall when said means is engagedtherewith; a fluid inlet in said means for admitting said fluid samplefrom the isolated area of borehole wall; a fluid channel communicatingbetween said inlet and said cylinder; motive means in said support formoving said means into engagement with the wall of the borehole inresponse to signal communicated from the earths surface; a piston insaid cylinder displaceable therein in response to formation samplefluids entering said cylinder, said piston including means responsive tothe pressure of formation sample fluid exerted thereon in said cylinderto variably opposed displacement of said piston in direct proportion tosaid pressure,

3. A device for obtaining samples of the fluid content of formationstraversed by a borehole comprising: a support adapted to be suspended ina borehole from the earths surface; a cylinder in said support forreceiving a fluid sample; means mounted on said support for isolating anarea of borehole wall when engaged therewith; a fluid inlet in saidmeans for admitting a fluid sample from that portion of the boreholewall engaged by said means; a fluid channel communicating between saidinlet and said chamber; motive means in said support for moving thefirst-mentioned means into engagement with the wall of the borehole inresponse to signal communicated from the earths surface; a piston insealed relation within said cylinder and displaceable with respectthereto in response to entry of formation sample fluid into saidcylinder; and means responsive to pressure of sample fluids in saidcylinder and connected with said piston for applying a braking forcebetween said piston and cylinder which varies directly with saidpressure, to the end that displacement of said piston in said cylinderis opposed and said sample fluid is constrained to do work in proportionto its pressure energy upon entering said cylinder.

4. A device for obtaining samples of the fluid content of formationstraversed by a borehole comprising: a support adapted to be suspended ina well borehole by means of a wireline from the earths surface; acylinder in said support for receiving a fluid sample; means mounted onsaid support for isolating an area of borehole wall when engagedtherewith; a fluid inlet in said means for admitting a fluid sample fromthat portion of the borehole wall engaged by said means; a fluid channelcommunicating between said inlet and said chamber; motive means in saidsupport for moving the first-mentioned means into engagement with thewall of the borehole in response to signal communicated from the earthssurface; a member extending longitudinally within said cylinder andsecured to one end of the same; a piston in sealed relation to saidcylinder and said member and displaceable with respect to both inresponse to entry of formation sample fluid into said cylinder; andmeans in said cylinder actuatable in response to the pressure of samplefluid therein for applying a cold working force between said piston andsaid member which varies directly with said pressure, to the end that abraking force is applied intermediate said piston and member to impededisplacement of said piston and constrain said sample fluid to do workin proportion to its pressure energy in entering said cylinder.

5. An actuator adapted for lowering within a borehole in connection witha device for engaging the borehole wall and for securing the operationthereof comprising: a support adapted for lowering in a borehole; atoggle mechanism, for connection with said device, connected with saidsupport for movement and operation of said device; a quantity ofpressurized gas contained in said support; and means in said supportconnected with said toggle mechanism for expanding and reducing thepressure of said gas in proportion to said movement and for applying theforce thereof to said toggle mechanism, whereby said device is operatedwith substantially uniform force without regard for the magnitude ofsaid movement, said means including a piston rod mounting three pistons,a first of said pistons operating in a first piston chamber, a second ofsaid pistons operating in a second piston chamber, a third of saidpistons operating in a third piston chamber, means for applying said gasto said first chamber to act on one side of said first piston to movesaid piston rod, conduit means interconnecting said second and thirdchambers, fluid within said second and third chambers transferredbetween said second and third chambers, upon movement of said pistonrod, said fluid acting on one side of said second piston, said togglemechanism being connected to said piston rod.-

6. An actuator as set forth in claim 5, in which said toggle mechanismis connected to said piston rod at a point intermediate said second andthird pistons.

7. An actuator as set forth in claim 5, in which fluid flow restrictionmeans is interposed in said conduit means.

8. An actuator as set forth in claim 5, in which said conduit meanscomprises a passageway through said piston rod.

9. An actuator as set forth in claim 5, including means forintercommunicating opposite sides of said first piston in said firstpiston chamber.

10. An actuator as set forth in claim 5, including means forintercommunicating the other side of said second piston with boreholefluid.

11. A device for establishing fluid communication between a formationtraversed by a borehole and a fluid chamber in said device comprising: asupport adapted to pass through a borehole; a fluid chamber in saidsupport; means on said support for engaging the wall of the borehole,for isolating a portion thereof from the fluid of said column and forestablishing fluid communication between said portion and said meanswhen the same is so engaged; a fluid channel connecting said means andsaid fluid chamber; a toggle mechanism connected with said support andthe first-mentioned means for movement thereof toward engagement withthe wall of the borehole, said toggle mechanism being characterized by amechanical advantage which increases with increases in said movement; aquantity of gas contained in said support; and means in said supportresponsive to surface control for expanding and reducing the pressure ofsaid gas in proportion to said movement and for applying the forcethereof to said toggle mechanism whereby the first-mentioned means isurged into engagement with the borehole wall with substantially uniformforce and with substantial independence of the amount of said movement,the last mentioned means including a piston rod mounting three pistons,a first of said pistons operating in a-first piston chamber, a second ofsaid pistons operating in a second piston chamber, a third of saidpistons operating in a third piston chamber, means for applying said gasto said first piston chamber to act on one side of said first piston tomove said piston rod, conduit means interconnecting said second andthird chambers, fluid within said second and third chambers transferredbetween said second and third chambers upon movement of said piston rod,said fluid acting on one side of said second piston, said togglemechanism being connected to said piston rod.

12. An actuator device adapted for employment within a boreholecontaining a column of fluid comprising: a support adapted for loweringwithin said borehole; first, second, and third cylinders in saidsupport; first, second, and third pistons, in sealed slidable engagementrespectively in said first, second, and third cylinders and definingfirst and second space portions in each; a force transmitting memberextending within all of said cylinders in sealed slidable engagementwith the walls of each and mechanically coupling said pistons; aquantity of gas contained in said support; means in said support forexpanding said gas in the first space portion of said first cylinder topower a first stroke of said first piston and force transmitting member;a normally open fluid channel including fluid throttling meanscommunicating between the first space portions of said second and thirdcylinders and defining therewith a space substantially filled with abuffer fluid adapted to meter between said second and third cylindersresponsive to movement of said force transmitting member; a normallyblocked fluid channel interconnecting the first and second spaceportions of said first cylinder; means in said support for unblockingsaid normally blocked channel and communicating the first and secondspace portions of said first cylinder to equalize any pressure force ofsaid gas therein and for admitting the pressure of borehole fluid to thesecond space portion of one of said second or third cylinders, whereuponsaid buffer fluid is displaced from the first space portion of 20 saidone cylinder to the first space portion of the other of said second orthird cylinders to act on the piston therein and effectuate a reversestroke of said force transmitting member; and means coupled to saidforce transmitting member for extracting useful force from a strokethereof.

References Cited by the Examiner UNITED STATES PATENTS 2,537,413 1/1951Lawrence l6698 2,540,123 2/1951 Kinley 16655.1 2,674,313 4/1954 Chambersl66-10O 2,692,023 10/1954 Conrad 16663 2,797,892 7/1957- Ryan 102202,915,123 12/1959 Lebourg 166100 3,079,793 3/1963 Le Bus et al 1661003,104,712 9/1963 Whitten 16655.1

BENJAMIN HERSH, Primary Examiner.

1. A DEVICE FOR OBTAINING SAMPLES OF THE FLUID CONTENT OF FORMATIONSTRAVERSED BY A BOREHOLE CONTAINING A COLUMN OF FLUID COMPRISING: ASUPPORT ADAPTED TO BE SUSPENDED IN A BOREHOLE BY MEANS OF A WIRELINEFROM THE EARTH''S SURFACE; A CHAMBER IN SAID SUPPORT FOR RECEIVING AFLUID SAMPLE; MEANS MOUNTED ON SAID SUPPORT ADAPTED TO ISOLATE AN AREAOF BOREHOLE WALL WHEN ENGAGED THEREWITH; MOTIVE MEANS IN SAID SUPPORTFOR MOVING SAID MEANS INTO ENGAGEMENT WITH THE WALL OF THE BOREHOLE; ANINLET MEMBER IN THE FIRST-MENTIONED MEANS HAVING WALLS ADAPTED FOREXPOSURE TO AND FOR WITHSTANDING THE PRESSURE OF SAID COLUMN OF FLUID; ACHARGE OF EXPLOSIVE MATERIAL, SHAPED FOR PRODUCING A JET STREAM WHENDETONED, SAID CHARGE BEING HOUSED IN SAID INLET MEMBER IN SPACEDRELATION TO SAID WALLS AND NORMALLY CLOSING SAID INLET MEMBER ANDPREVENTING BOREHOLE FLUIDS FROM ENTERING SAID CHAMBER; MEANS IN SAIDINLET MEMBER FOR DETONATING SAID CHARGE; A SPACER DISPOSED ABOUT SAIDCHARGE WITHIN SAID INLET FOR MAINTAINING SAID SPACED RELATION COMPRISESOF POROUS MATERIAL; AND A FLUID CHANNEL COMMUNICATING BETWEEN SAID INLETMEMBER AND SAID CHAMBER, SAID CHARGE WHEN DETONATED ADAPTED TO RADIALLYCOMPRESS SAID POROUS MATERIAL AGAINST THE WALLS OF SAID INLET MEMBER,WHEREBY FLUID COMMUNICATION IS ESTABLISHED THROUGH SAID INLET MEMBERBETWEEN THE FORMATION WITHIN SAID ISOLATED AREA AND SAID CHAMBER.
 2. ADEVICE FOR OBTAINING SAMPLE OF FLUID CONTENT OF FORMATIONS TRAVERSED BYA BOREHOLE COMPRISING: A SUPPORT ADAPTED TO BE SUSPENDED IN A BOREHOLEBY MEANS OF A WIRELINE FROM THE EARTH''S SURFACE; A CYLINDER IN SAIDSUPPORT FOR RECEIVING A FLUID SAMPLE; MEANS MOUNTED ON SAID SUPPORT FORISOLATING AN AREA OF BOREHOLE WALL WHEN SAID MEANS IS ENGAGED THEREWITH;A FLUID INLET IN SAID MEANS FOR ADMITTIN SAID FLUID SAMPLE FROM THEISOLATED AREA OF BOREHOLE WALL; A FLUID CHANNEL COMMUNICATING BETWEENSAID INLET AND SAID CYLINDER; MOTIVE MEANS IN SAID SUPPORT FOR MOVINGSAID MEANS INTO ENGAGEMENT WITH THE WALL OF THE BOREHOLE IN RESPONSE TOSIGNAL COMMUNICATED FROM THE EARTH''S SURFACE; A PISTON IN SAID CYLINDERDISPLACEABLE THEREIN IN RESPONSE TO FORMATION SAMPLE FLUIDS ENTERINGSAID CYLINDER, SAID PISTON INCLUDING MEANS RESPONSIVE TO THE PRESSURE OFFORMATION SAMPLE FLUID EXERTED THEREON IN SAID CYLINDR TO VARIABLYOPPOSED DISPLACEMENT OF SAID PISTON IN DIRECT PROPORTION TO SAIDPRESSURE.